/*
 * Serial back end (Windows-specific).
 */

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

#include "putty.h"

#define SERIAL_MAX_BACKLOG 4096

typedef struct serial_backend_data {
  HANDLE port;
  struct handle *out, *in;
  void *frontend;
  int bufsize;
  long clearbreak_time;
  int break_in_progress;
} * Serial;

static void serial_terminate(Serial serial)
{
  if (serial->out) {
    handle_free(serial->out);
    serial->out = NULL;
  }
  if (serial->in) {
    handle_free(serial->in);
    serial->in = NULL;
  }
  if (serial->port != INVALID_HANDLE_VALUE) {
    if (serial->break_in_progress)
      ClearCommBreak(serial->port);
    CloseHandle(serial->port);
    serial->port = INVALID_HANDLE_VALUE;
  }
}

static int serial_gotdata(struct handle *h, void *data, int len)
{
  Serial serial = (Serial)handle_get_privdata(h);
  if (len <= 0) {
    const char *error_msg;

    /*
     * Currently, len==0 should never happen because we're
     * ignoring EOFs. However, it seems not totally impossible
     * that this same back end might be usable to talk to named
     * pipes or some other non-serial device, in which case EOF
     * may become meaningful here.
     */
    if (len == 0)
      error_msg = "End of file reading from serial device";
    else
      error_msg = "Error reading from serial device";

    serial_terminate(serial);

    notify_remote_exit(serial->frontend);

    logevent(serial->frontend, error_msg);

    connection_fatal(serial->frontend, "%s", error_msg);

    return 0; /* placate optimiser */
  } else {
    return from_backend(serial->frontend, 0, data, len);
  }
}

static void serial_sentdata(struct handle *h, int new_backlog)
{
  Serial serial = (Serial)handle_get_privdata(h);
  if (new_backlog < 0) {
    const char *error_msg = "Error writing to serial device";

    serial_terminate(serial);

    notify_remote_exit(serial->frontend);

    logevent(serial->frontend, error_msg);

    connection_fatal(serial->frontend, "%s", error_msg);
  } else {
    serial->bufsize = new_backlog;
  }
}

static const char *serial_configure(Serial serial, HANDLE serport, Conf *conf)
{
  DCB dcb;
  COMMTIMEOUTS timeouts;

  /*
   * Set up the serial port parameters. If we can't even
   * GetCommState, we ignore the problem on the grounds that the
   * user might have pointed us at some other type of two-way
   * device instead of a serial port.
   */
  if (GetCommState(serport, &dcb)) {
    char *msg;
    const char *str;

    /*
     * Boilerplate.
     */
    dcb.fBinary = TRUE;
    dcb.fDtrControl = DTR_CONTROL_ENABLE;
    dcb.fDsrSensitivity = FALSE;
    dcb.fTXContinueOnXoff = FALSE;
    dcb.fOutX = FALSE;
    dcb.fInX = FALSE;
    dcb.fErrorChar = FALSE;
    dcb.fNull = FALSE;
    dcb.fRtsControl = RTS_CONTROL_ENABLE;
    dcb.fAbortOnError = FALSE;
    dcb.fOutxCtsFlow = FALSE;
    dcb.fOutxDsrFlow = FALSE;

    /*
     * Configurable parameters.
     */
    dcb.BaudRate = conf_get_int(conf, CONF_serspeed);
    msg = dupprintf("Configuring baud rate %lu", dcb.BaudRate);
    logevent(serial->frontend, msg);
    sfree(msg);

    dcb.ByteSize = conf_get_int(conf, CONF_serdatabits);
    msg = dupprintf("Configuring %u data bits", dcb.ByteSize);
    logevent(serial->frontend, msg);
    sfree(msg);

    switch (conf_get_int(conf, CONF_serstopbits)) {
    case 2:
      dcb.StopBits = ONESTOPBIT;
      str = "1";
      break;
    case 3:
      dcb.StopBits = ONE5STOPBITS;
      str = "1.5";
      break;
    case 4:
      dcb.StopBits = TWOSTOPBITS;
      str = "2";
      break;
    default:
      return "Invalid number of stop bits (need 1, 1.5 or 2)";
    }
    msg = dupprintf("Configuring %s data bits", str);
    logevent(serial->frontend, msg);
    sfree(msg);

    switch (conf_get_int(conf, CONF_serparity)) {
    case SER_PAR_NONE:
      dcb.Parity = NOPARITY;
      str = "no";
      break;
    case SER_PAR_ODD:
      dcb.Parity = ODDPARITY;
      str = "odd";
      break;
    case SER_PAR_EVEN:
      dcb.Parity = EVENPARITY;
      str = "even";
      break;
    case SER_PAR_MARK:
      dcb.Parity = MARKPARITY;
      str = "mark";
      break;
    case SER_PAR_SPACE:
      dcb.Parity = SPACEPARITY;
      str = "space";
      break;
    }
    msg = dupprintf("Configuring %s parity", str);
    logevent(serial->frontend, msg);
    sfree(msg);

    switch (conf_get_int(conf, CONF_serflow)) {
    case SER_FLOW_NONE:
      str = "no";
      break;
    case SER_FLOW_XONXOFF:
      dcb.fOutX = dcb.fInX = TRUE;
      str = "XON/XOFF";
      break;
    case SER_FLOW_RTSCTS:
      dcb.fRtsControl = RTS_CONTROL_HANDSHAKE;
      dcb.fOutxCtsFlow = TRUE;
      str = "RTS/CTS";
      break;
    case SER_FLOW_DSRDTR:
      dcb.fDtrControl = DTR_CONTROL_HANDSHAKE;
      dcb.fOutxDsrFlow = TRUE;
      str = "DSR/DTR";
      break;
    }
    msg = dupprintf("Configuring %s flow control", str);
    logevent(serial->frontend, msg);
    sfree(msg);

    if (!SetCommState(serport, &dcb))
      return "Unable to configure serial port";

    timeouts.ReadIntervalTimeout = 1;
    timeouts.ReadTotalTimeoutMultiplier = 0;
    timeouts.ReadTotalTimeoutConstant = 0;
    timeouts.WriteTotalTimeoutMultiplier = 0;
    timeouts.WriteTotalTimeoutConstant = 0;
    if (!SetCommTimeouts(serport, &timeouts))
      return "Unable to configure serial timeouts";
  }

  return NULL;
}

/*
 * Called to set up the serial connection.
 *
 * Returns an error message, or NULL on success.
 *
 * Also places the canonical host name into `realhost'. It must be
 * freed by the caller.
 */
static const char *serial_init(void *frontend_handle,
                               void **backend_handle,
                               Conf *conf,
                               const char *host,
                               int port,
                               char **realhost,
                               int nodelay,
                               int keepalive)
{
  Serial serial;
  HANDLE serport;
  const char *err;
  char *serline;

  serial = snew(struct serial_backend_data);
  serial->port = INVALID_HANDLE_VALUE;
  serial->out = serial->in = NULL;
  serial->bufsize = 0;
  serial->break_in_progress = FALSE;
  *backend_handle = serial;

  serial->frontend = frontend_handle;

  serline = conf_get_str(conf, CONF_serline);
  {
    char *msg = dupprintf("Opening serial device %s", serline);
    logevent(serial->frontend, msg);
    sfree(msg);
  }

  {
    /*
     * Munge the string supplied by the user into a Windows filename.
     *
     * Windows supports opening a few "legacy" devices (including
     * COM1-9) by specifying their names verbatim as a filename to
     * open. (Thus, no files can ever have these names. See
     * <http://msdn2.microsoft.com/en-us/library/aa365247.aspx>
     * ("Naming a File") for the complete list of reserved names.)
     *
     * However, this doesn't let you get at devices COM10 and above.
     * For that, you need to specify a filename like "\\.\COM10".
     * This is also necessary for special serial and serial-like
     * devices such as \\.\WCEUSBSH001. It also works for the "legacy"
     * names, so you can do \\.\COM1 (verified as far back as Win95).
     * See <http://msdn2.microsoft.com/en-us/library/aa363858.aspx>
     * (CreateFile() docs).
     *
     * So, we believe that prepending "\\.\" should always be the
     * Right Thing. However, just in case someone finds something to
     * talk to that doesn't exist under there, if the serial line
     * contains a backslash, we use it verbatim. (This also lets
     * existing configurations using \\.\ continue working.)
     */
    char *serfilename =
        dupprintf("%s%s", strchr(serline, '\\') ? "" : "\\\\.\\", serline);
    serport = CreateFile(serfilename,
                         GENERIC_READ | GENERIC_WRITE,
                         0,
                         NULL,
                         OPEN_EXISTING,
                         FILE_FLAG_OVERLAPPED,
                         NULL);
    sfree(serfilename);
  }

  if (serport == INVALID_HANDLE_VALUE)
    return "Unable to open serial port";

  err = serial_configure(serial, serport, conf);
  if (err)
    return err;

  serial->port = serport;
  serial->out = handle_output_new(
      serport, serial_sentdata, serial, HANDLE_FLAG_OVERLAPPED);
  serial->in = handle_input_new(serport,
                                serial_gotdata,
                                serial,
                                HANDLE_FLAG_OVERLAPPED | HANDLE_FLAG_IGNOREEOF |
                                    HANDLE_FLAG_UNITBUFFER);

  *realhost = dupstr(serline);

  /*
   * Specials are always available.
   */
  update_specials_menu(serial->frontend);

  return NULL;
}

static void serial_free(void *handle)
{
  Serial serial = (Serial)handle;

  serial_terminate(serial);
  expire_timer_context(serial);
  sfree(serial);
}

static void serial_reconfig(void *handle, Conf *conf)
{
  Serial serial = (Serial)handle;
  const char *err;

  err = serial_configure(serial, serial->port, conf);

  /*
   * FIXME: what should we do if err returns something?
   */
}

/*
 * Called to send data down the serial connection.
 */
static int serial_send(void *handle, const char *buf, int len)
{
  Serial serial = (Serial)handle;

  if (serial->out == NULL)
    return 0;

  serial->bufsize = handle_write(serial->out, buf, len);
  return serial->bufsize;
}

/*
 * Called to query the current sendability status.
 */
static int serial_sendbuffer(void *handle)
{
  Serial serial = (Serial)handle;
  return serial->bufsize;
}

/*
 * Called to set the size of the window
 */
static void serial_size(void *handle, int width, int height)
{
  /* Do nothing! */
  return;
}

static void serbreak_timer(void *ctx, unsigned long now)
{
  Serial serial = (Serial)ctx;

  if (now == serial->clearbreak_time && serial->port) {
    ClearCommBreak(serial->port);
    serial->break_in_progress = FALSE;
    logevent(serial->frontend, "Finished serial break");
  }
}

/*
 * Send serial special codes.
 */
static void serial_special(void *handle, Telnet_Special code)
{
  Serial serial = (Serial)handle;

  if (serial->port && code == TS_BRK) {
    logevent(serial->frontend, "Starting serial break at user request");
    SetCommBreak(serial->port);
    /*
     * To send a serial break on Windows, we call SetCommBreak
     * to begin the break, then wait a bit, and then call
     * ClearCommBreak to finish it. Hence, I must use timing.c
     * to arrange a callback when it's time to do the latter.
     *
     * SUS says that a default break length must be between 1/4
     * and 1/2 second. FreeBSD apparently goes with 2/5 second,
     * and so will I.
     */
    serial->clearbreak_time =
        schedule_timer(TICKSPERSEC * 2 / 5, serbreak_timer, serial);
    serial->break_in_progress = TRUE;
  }

  return;
}

/*
 * Return a list of the special codes that make sense in this
 * protocol.
 */
static const struct telnet_special *serial_get_specials(void *handle)
{
  static const struct telnet_special specials[] = {{"Break", TS_BRK},
                                                   {NULL, TS_EXITMENU}};
  return specials;
}

static int serial_connected(void *handle)
{
  return 1; /* always connected */
}

static int serial_sendok(void *handle)
{
  return 1;
}

static void serial_unthrottle(void *handle, int backlog)
{
  Serial serial = (Serial)handle;
  if (serial->in)
    handle_unthrottle(serial->in, backlog);
}

static int serial_ldisc(void *handle, int option)
{
  /*
   * Local editing and local echo are off by default.
   */
  return 0;
}

static void serial_provide_ldisc(void *handle, void *ldisc)
{
  /* This is a stub. */
}

static void serial_provide_logctx(void *handle, void *logctx)
{
  /* This is a stub. */
}

static int serial_exitcode(void *handle)
{
  Serial serial = (Serial)handle;
  if (serial->port != INVALID_HANDLE_VALUE)
    return -1; /* still connected */
  else
    /* Exit codes are a meaningless concept with serial ports */
    return INT_MAX;
}

/*
 * cfg_info for Serial does nothing at all.
 */
static int serial_cfg_info(void *handle)
{
  return 0;
}

Backend serial_backend = {serial_init,
                          serial_free,
                          serial_reconfig,
                          serial_send,
                          serial_sendbuffer,
                          serial_size,
                          serial_special,
                          serial_get_specials,
                          serial_connected,
                          serial_exitcode,
                          serial_sendok,
                          serial_ldisc,
                          serial_provide_ldisc,
                          serial_provide_logctx,
                          serial_unthrottle,
                          serial_cfg_info,
                          NULL /* test_for_upstream */,
                          "serial",
                          PROT_SERIAL,
                          0};
